feat(docs): Add comprehensive documentation for Vexer, Vulnerability Explorer, and Zastava modules

- Introduced AGENTS.md, README.md, TASKS.md, and implementation_plan.md for Vexer, detailing mission, responsibilities, key components, and operational notes.
- Established similar documentation structure for Vulnerability Explorer and Zastava modules, including their respective workflows, integrations, and observability notes.
- Created risk scoring profiles documentation outlining the core workflow, factor model, governance, and deliverables.
- Ensured all modules adhere to the Aggregation-Only Contract and maintain determinism and provenance in outputs.

docs/modules/cli/implementation_plan.md

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+# Implementation plan — CLI
+
+## Current objectives
+- Maintain deterministic behaviour and offline parity across releases.
+- Keep documentation, telemetry, and runbooks aligned with the latest sprint outcomes.
+
+## Workstreams
+- Backlog grooming: reconcile open stories in ../../TASKS.md with this module's roadmap.
+- Implementation: collaborate with service owners to land feature work defined in SPRINTS/EPIC docs.
+- Validation: extend tests/fixtures to preserve determinism and provenance requirements.
+
+## Epic milestones
+- **Epic 2 – Policy Engine & Editor:** deliver deterministic policy verbs, simulation, and explain outputs.
+- **Epic 4 – Policy Studio:** add registry/promotion workflows, lint tooling, and approvals UX.
+- **Epic 6 – Vulnerability Explorer:** integrate ledger/triage operations.
+- **Epic 10 – Export Center:** automate export verification and Offline Kit flows.
+- **Epic 11 – Notifications Studio:** manage rule/channel authoring and previews via CLI.
+- Track CLI-specific work (e.g., CLI-CORE-41-001, DOCS-CLI-OBS-52-001) in ../../TASKS.md and src/Cli/**/TASKS.md.
+
+## Coordination
+- Review ./AGENTS.md before picking up new work.
+- Sync with cross-cutting teams noted in ../../implplan/SPRINTS.md.
+- Update this plan whenever scope, dependencies, or guardrails change.